Gas turbine engines typically include a fan section, a compressor section, a combustion section, and a turbine section in serial flow relationship. Air drawn in by the fan section is compressed or pressurized in the compressor section before being heated in the combustion section to produce a high velocity gas stream. Energy is extracted from the gas stream in the turbine section by being utilized to cause rotation of a plurality of rotor stages. Each rotor stage comprises an annular array of rotor blades and receives combustion gases from an upstream adjacent annular array of nozzle vanes. The rotor blades are secured to a rotor disk which rotates as the gas stream passes over the rotor blades. The nozzle vanes are stationary and turn the gas stream in a desired direction over the rotor blades.
The temperature of the gas stream as it exits the combustion section may be as high as, for example, 2000 degrees Fahrenheit (or 1093 degrees Centigrade). This stream of hot gases may attain a velocity, for example, in excess of 2000 feet per second (or 610 meters per second) as it passes through the nozzle vanes. The nozzle vanes are suitably attached to an inner band or platform and an outer band or shroud, such as, for example, by welding or being integrally cast therewith to form an annular array of vanes commonly referred to as a turbine nozzle. Since the turbine nozzle directs the gas stream in predetermined directions for efficient operation of the engine, it is desirable to assure that all of the gas stream passes through the vanes of the nozzle by reducing leakage around the platform and shroud ends of the nozzle.
It is known in the art to provide seals to prevent gas leakage in gas turbine engines. U.S. Pat. No. 3,423,070 issued Jan. 21, 1969 and assigned to the assignee of the present invention describes one form of seal, i.e., a honeycomb seal. One disadvantage with prior art seal arrangements has been the difficulty of replacing seals during engine servicing. For example, seals have been brazed or welded to the nozzle bands. A further disadvantage arises from other forms of attachment by either rivets or pins which may be required to permit radial shifting of the seal. Such radial shifting is utilized to compensate for differential thermal expansion and contraction in the turbine section. When rivets and pins are used, the support structure for the seal is relatively heavy and costly and decreases the fuel efficiency of the engine. Another disadvantage of the prior art seal arrangements has been the requirement for special tooling for installing and handling pins and/or rivets.